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arXiv · 2109.03599

Phonon Stability of Quantum Droplets in a dipolar Bose gases

Fan Zhang·Lan Yin
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Abstract

Stabilized by quantum fluctuations, dipolar Bose-Einstein condensates can form self-bound liquidlike droplets in the mean-field unstable regime. However in the Bogoliubov theory, some phonon energies are imaginary in the long-wavelength limit, implying dynamical instability of this system. A similar instability appears in the Bogoliubov theory of a binary quantum droplet, and is removed due to higher-order quantum fluctuations as shown recently [1]. In this work, we study the phonon energy of a dipolar quantum droplet in the Beliaev formalism, and find that quantum fluctuations can enhance the phonon stability. We obtain the anisotropic sound velocity which can be tested in experiment.

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Fan Zhang, Lan Yin. 2021-09-08. Phonon Stability of Quantum Droplets in a dipolar Bose gases. https://doi.org/10.1088/0256-307x%2F39%2F6%2F060301

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